A system for performing conversation over a wireless LAN by using a handy transceiver type mobile terminal device and a server for relaying a communication has been put into practice (see Non-Patent Literature 1). In this voice communication system, since a voice signal is compressed and packetized for transmission/reception, a plurality of speeches can be transmitted at the same time.
The conversation between the terminal devices can be performed not only in a half-duplex mode similar to the conventional wireless transceiver but also in a full-duplex mode in which a plurality of terminal devices can speak at the same time as in telephone since packet communication is used as described above. The voices made at the same time are mixed by the server and delivered to the communicating terminal devices.